The purpose of this phase Ib clinical trial is to evaluate the safety of the combination of INC424 and BKM120 in the myelofibrosis population and to establish the maximum tolerated dose and or the Recommended Phase II dose of the combination guided by the Bayesian dose escalation model. INC424 has shown efficacy in myelofibrosis (MF) and is approved in the US and EU for the treatment of MF. BKM120 is a PI3K inhibitor. Preclinical and early clinical experience support inhibition of the PI3K/mTOR pathway in MF as aberrant activation of the pathway has been observed in MF models and may contribute to the pathogenesis of the disease.